This invention generally relates to a method for improved aeration for septic tanks and the like.
Bacterial breakdown of sewage waste material is essentially performed by one of two basic processes, namely an aerobic process and an anaerobic process. The aerobic process requires oxygen for the bacteria to survive and successfully decompose waste material. Emphasis upon the aerobic action, as opposed to anaerobic bacterial action is preferred because aerobic bacteria decompose waste materials often without objectionable odors or the formation of objectionable gases. Aerobic bacteria need a constant supply of oxygen on which to thrive, and therefore, such aerobic systems require continuous replenishment of dissolved oxygen consumed by the aerobes in the waste material. Additionally, agitation is necessary to prohibit waste particles from settling out to resist bacterial decomposition and form a continual buildup of sludge in septic tanks and the like.
These requirements of aerobic systems have given rise to numerous mechanical aerators and agitators, including designs similar to those used in commercial sewage treatment plants. For example, devices have been designed to aerate the material by rotating paddle wheels or the like which operate to either beat air into the material while moving it in the reservoir or to at least partially throw the material into the air. Other designs have incorporated separate means for moving the material in the reservoir and have introduced air by pumping compressed air through permeable "air stones" positioned at the bottom of the reservoir. The air stones are adapted to break the air into bubbles which enter the waste material. Bubbles are preferred over a stream of air passing through the material because the ratio of surface area to volume is greater and enables the oxygen to be more easily dissolved in the material. The proper functioning of an aerobic system is, of course, dependent upon the quantity of dissolved oxygen that is present within the waste material. It is seen that more power would be consumed by injecting larger than necessary quantities of oxygen into the material and, therefore, economic considerations are important in the manner in which oxygen is introduced. Another important economic consideration involves the manner in which the material is moved around or circulated within the reservoir.
Prior induced aeration systems most often insert air under pressure into the waste mass which is being "broken up" simultaneously by agitation. As a result air becomes entrapped and bubbles form. However, because the air is under pressure and the liquid agitated, the bubbles formed are quite large. As a result they quickly rise to the surface and escape. This results in less than ideal sludge contact with the oxygen supply of the air. Thus, the amount of dissolved oxygen available for the aerobic bacteria is less then it might be if contact were prolonged.
A prior invention of one of the inventors (Blough), U.S. Pat. No. 3,778,233, relates to an improved device for aeration used primarily in confinement livestock operations to aerate sludge pits used in conjunction with such livestock operations. While that device works fine under the circumstances of confinement feeding operations for livestock, such as hogs, there are limitations with use of such a device in conjunction with septic tanks that are used for storing human waste.
One of the problems with sewage disposal plants, and septic tank plants are that often the disposal system finds itself "contaminated" with non-organic non-biodegradable waste materials such as band-aids, sanitary napkins, disposable diapers, condoms, and other material that people often discard into the lines of a sewage system. These adulterating materials can be drawn into the propeller of an aeration device such as that described in my previous U.S. Pat. No. 3,778,233. As a result, the propeller often will become entangled in these materials, and the materials will plug the air tube lines. As a result, aeration is not successfully achieved, and at best the sludge material is simply generally stirred or agitated by the propeller with little effect on biodegradation. There is, therefore, a continuing need for an improved aeration device of the general type disclosed in my previous U.S. Pat. No. 3,778,233, but of a design which is improved so that it can be used successfully for aeration in septic tanks that contain the above-referred to "contaminating" non-organic, non-biodegradable waste materials.
The development of such a device as now patented in Ser. No. 687,373, filed Apr. 18, 1991, now U.S. Pat. No. 5,194,144 would mean that septic tanks can be conveniently converted into aeration units so that aerobic bacteria may decompose the material within the septic tanks, such that it can be successfully used for uses such as yard fertilizer, etc.
A primary objective of the present invention is to provide an improved aeration process of the type generally described in the above patent so that it can be used for successful vacuum aeration of septic tanks to provide low pressure microbubbles which are retained for longer hold times in a septic tank.
Another objective of the present invention is to provide an aeration method which provides ultra fine bubbles under equilibrium pressure with the liquid media for aeration of septic material, so that they do not rapidly rise to the surface and exit the tank.
An even further objective of the present invention is to provide an aeration method which will keep the dissolved oxygen content in septic tanks between 6 ppm and 10 ppm at all times to allow immediate conversation of all sizes of organic material particles by aerobic bacteria.
An even further objective of the present invention is to provide an aeration method which allows a home septic tank to be inexpensively converted into an aeration unit for decomposition of human organic waste material.
The method and means of accomplishing these as well as other objectives of the invention will become apparent from the detailed description of the invention which follows hereinafter.